Japanese publication No. JP-Hei 9-226090, published Sep. 2, 1997, discloses a spray type dampening unit and detector. To rapidly and accurately detected defective printed matter by providing a light emitting part which emits light to a jet of water and a light receiving part which receives the light transmitted through the water near the injection aperture of a wetting water supply nozzle on an offset rotary press, the wetting water is detected by a water detecting part based on a signal from the light receiving part. A light emitting part consisting of a modulator, a cable and a light emitter and a light receiving part consists of a light receiver, an amplifier and an A/D converter which are grouped together. About 95% of the quantity of light emitted to a wetting water from the light emitter is transmitted through the wetting water and the quantity of the received light is measured by the light receiver. The light being emitted by the light emitter is perpendicularly projected to the water level of the wetting water. The light receiver has a photoelectric conversion element and a voltage to be output by the conversion element, amplified by the amplifier, as the voltage is very low. Furthermore, the voltage is subjected to an A/D conversion process. A controller receives an output signal from the light receiving part and a wetting water supply signal to be given to a wetting water supply device and determines whether or not the wetting water is actually supplied.
In Japanese publication JP-Hei 9-220802, published on Aug. 26,1997, likewise a spray type dampening unit and detector is disclosed. Ring water injection nozzles are provided at almost a specified interval, and a set of a generator and a wave receiving part are installed near the jet aperture of the wetting water injection nozzle. An energy wave which is projected from the generator for generating a low or a high frequency wave, an ultrasonic wave or an air pressure wave is emitted to the water level of the wetting water, being transmitted through the wetting water and reflected by a reflecting part. In addition, the energy wave is reflected by the surface of the wetting water and is received by a wave receiving part. At the wave receiving part the energy wave is subjected to an AID conversion after amplification.
Both Japanese documents show a protective element which surrounds the dampening fluids spray nozzles and which is assigned to a respective cylinder. However, both disclosures are silent with regard to mist containment.
Spray dampeners are well known in the cold set printing industry. Existing embodiments of mist containment systems consist of tightly fitting shields which create physical barriers to contain the mist. At the onset of misting some mist will escape the standard shielding. As more mists collects, the concentration inside the containment area increases until saturation. Once the air cannot hold anymore solution the mist either escapes through the gaps or is condensed on the inside surfaces of the shields where it collects. In the case where the spray is applied to a moving surface such as a cylinder, there must be a gap between the guard and the application surface. If this gap is too small any disturbances or vibrations can cause the guard to disrupt the surface. If the gap is too large, the mist will not be sufficiently contained and will defuse into the local environment. The basic problem with the existing embodiments is that they do not provide a controllable means for the removal of mist from the containment area. One approach to eliminate the above-mentioned deficiencies of the known solution was to minimize the gaps on existing mist containment shields, in order to restrict the release of mist. Some embodiments include a gravity fed drain where the pooled up solution can exit the mist containment area without flowing onto critical portions of the machine, where they detrimentally can affect the quality of the freshly produced printed product.